Many illnesses or conditions require a constant level of medicaments or agents in vivo to provide the most effective prophylactic, therapeutic or diagnostic results. In the past, medicaments were given in doses at intervals which resulted in fluctuating medication levels.
Attempts to control and steady medication levels have more recently included the use of many biodegradable substances, such as polymeric and protein microspheres containing the medicament. The use of these microspheres provided an improvement in the controlled release of medicaments by utilizing the inherent biodegradability of the polymer to improve the release of the medicament and provide a more even, controlled level of medication.
However, many of these methods result in low yields of microspheres due to a combination of the methods and apparatus used. Further, some processes cannot be scaled-up from experimental level to a commercial production level.
Therefore, a need exists for a method of forming microspheres with lower losses of biologically active agent, high product yields, and commercial-scale feasibility.
This invention relates to a method for forming microparticles of a material from microdroplets of a solution, wherein the solution comprises the material dissolved in a solvent. The method includes the steps of directing the microdroplets into a freezing zone, wherein the freezing zone is surrounded by a liquified gas, and wherein the microdroplets freeze. The frozen microdroplets are then mixed with a liquid non-solvent, whereby the solvent is then extracted into the non-solvent, thereby forming the microparticles.
This invention has numerous advantages, for instance, this method and apparatus provides high yields, commercial production levels of controlled release microparticles, an enclosed system for aseptic processing, microparticle size control and process control reproducibility.
In addition, the method of invention permits greater tailoring of temperature profiles during performance of the method.